JPS5953000B2 - Seal structure of rotating plug in nuclear reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealing structure for a rotating plug that shields an upper opening of a reactor vessel in a nuclear reactor.

A fast breeder nuclear reactor is known in which the upper opening of the reactor vessel is shielded with a rotating plug.

In other words, this rotating plug has a control rod drive device that is positioned on the center line of the reactor vessel, and is also equipped with a fuel exchanger at an eccentric position, and when exchanging fuel, the control rods are moved from the control rod drive device into the core, and the control rods are The rotary plug is rotated with the output reduced, and the control rods are transferred to the fuel storage area surrounding the reactor core by a refueling machine.

Therefore, the rotating plug is rotatably attached to the opening of the furnace vessel, but the relationship between the rotating plug and the furnace vessel requires a strict seal to prevent leakage of the cover gas inside the furnace. do.

As this sealing structure, one using a liquid sealing material has been known from the past.

In other words, this device has a gutter-shaped saucer containing a liquid sealing material, which will be described later, formed around the entire circumference on either the inner periphery of the opening of the furnace vessel or the outer periphery of the rotary plug, and the other side is provided with a trough-shaped saucer containing the liquid sealing material in the saucer. A partition plate is formed around the entire circumference to be immersed inside the furnace vessel, and the airtightness inside the furnace vessel is maintained by these partition plates and a liquid sealant.

The above-mentioned liquid sealing material is a metal that is dissolved at room temperature, such as mercury, or a metal that is solidified (frozen) at room temperature, such as a low melting point alloy such as B1-3n.
The metal used is a metal that becomes a solution at a temperature of 0°C, and the latter remains in a solidified state during furnace operation or when the rotating plug is not rotating, and only when the rotating plug is rotated, it is heated with a heater and becomes a solution, and the partition It is used to allow movement of the plate.

However, with such a seal structure, if the cover gas pressure in the furnace fluctuates while the sealant is being dissolved, the liquid level of the sealant in the saucer will oscillate in response to the gas pressure, causing the gas pressure to fluctuate. When the amount of gas is extremely large, or when the natural frequency of the sealing liquid level matches the fluctuation period of the gas pressure and resonance occurs, the sealing material overflows from the saucer and jumps into the furnace vessel.

When liquid sealant overflows into the reactor vessel, it contaminates the cover gas and cooling fluid, changes the thermal and nuclear properties of the fluid, causes corrosion of structural materials, and precipitates as impurities that can damage the flow path. I'm used to blocking things.

This requires a liquid seal removal operation, which has the disadvantage of requiring an extremely large amount of labor.

Further, if the seal liquid level fluctuates violently, there is a problem in that the cover gas passes through the seal material and leaks to the outside.

This invention was made based on the above circumstances, and its purpose is to reduce the fluctuation of the liquid sealant in the saucer even when the cover gas pressure fluctuates, and to prevent the sealant from moving inside the furnace vessel. The present invention aims to provide a sealing structure for a rotating plug in a nuclear reactor that prevents leakage of cover gas and leakage of cover gas to the outside of the reactor.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the figure, 1 is a furnace vessel, which is covered with a shielding structure such as concrete.

A reactor core section 2 including fuel assemblies is provided within the reactor vessel 1, and a fuel storage section 3 is provided around the reactor core section 2.

The reactor core 2 is connected to an inlet pipe 4 that introduces a coolant such as sodium, and the solutes introduced through the inlet pipe 4 are heated in the reactor core 2 and exit from an outlet pipe 5. It looks like this.

The upper part of the furnace vessel 1 is open, and a fixing plug 6 is hermetically attached to this opening.

The fixed plug 6 is located vertically above the fuel storage section 3 and includes a fuel inlet/outlet device 7.

And this fixing plug 6 is attached to the central axis 01-0 of the furnace vessel 1.
An opening 8 having a center at a position 0°-02 eccentric from 1 is formed.

A rotary plug 9 is rotatably attached to this opening 8.

This rotary plug 9 is provided with a control rod drive device 10 that is located directly above the reactor core 2 when the rotary plug 9 rotates. The fuel exchanger 1 is moved directly above the
1 is attached.

A rotation bearing 12 is mounted between the rotating plug 9 and the fixed plug 6, and the rotary plug 9 is rotationally driven by a rotation drive device (not shown).

Note that 13 indicates a backup seal.

Thus, a seal portion 14 according to the present invention is formed between the fixed plug 6 and the rotating plug 9.

This seal portion 14 is shown enlarged in FIG. 2, and will be described below based on this.

That is, a gutter-like saucer 15 is formed on the inner peripheral surface of the opening 8 in the fixed plug 6 over the entire circumference, and this saucer 15 has a shape that gradually expands as it approaches the top, that is, as it moves upward. Both side surfaces 15a and 15b are configured to be inclined so that the horizontal area increases accordingly.

In this saucer 15, a low melting point metal of the B1-3n series, for example, is accommodated as a liquid sealing material 16.

On the other hand, a partition plate 1 is provided on the outer peripheral surface of the rotary plug 9 over the entire circumference.
7 is provided, and this partition plate 17 is immersed in the liquid sealing material 16 in the saucer 15.

Therefore, the inside of the saucer 15 is separated by the partition plate 17 into one seal chamber 18a connected to the cover gas inside the furnace vessel 1, and
It is divided into the other seal chamber 18b on the outside of the furnace.

The operation of the embodiment having such a configuration will be explained.

During operation, the control rod drive device 10 is positioned directly above the reactor core 2, and the output is controlled by operating control rods (not shown).

At this time, thorium as a coolant is led from the inlet pipe 4, cools the reactor core 2, and exits from the outlet pipe 5.

On the other hand, during fuel exchange, all control rods are removed from grippers (not shown) of the control rod drive device 10 and held in the reactor core 2.

After the output decreases, the rotary plug 9 is rotated to move the fuel exchanger 11 above the reactor core 2, take out the fuel at an arbitrary position, and then rotate the rotary plug 9 again to move the fuel exchanger 11 to
The spent fuel supported in the storage part 3 is transferred to the storage part 3, and the new fuel in the storage part 3 is supported and the new fuel is transferred to the reactor core part 2 by rotation of the rotary plug 9.

Further, the spent fuel in the storage section 3 is taken out of the furnace from the fuel inlet/output machine 7 and transferred to an external storage section.

In this way, the rotary plug 9 is driven to rotate as necessary, but in the seal portion 14, the rotary plug 9
Since the partition plate 17, which rotates integrally with the reactor, is immersed in the liquid sealant 16, airtightness is maintained by the liquid sealant 16, and the cover gas inside the furnace vessel 1 will not leak.

That is, the liquid sealing material 16 is solid at room temperature, but when heated by a heater prior to the rotation of the rotary plug 9, it becomes a solution, and thus allows the partition plate 17 to rotate. can be rotated.

However, when the cover gas pressure in the furnace vessel 1 suddenly decreases while the liquid sealant 16 is in solution, this decrease in gas pressure acts on one seal chamber 18a.

Therefore, the liquid level of the liquid sealing material 16 in this sealing chamber 18a rises, and in response to this, the liquid level in the other sealing chamber 18b becomes lower.

At this time, the opening area of one seal chamber 18a becomes wider as it goes upward, and the opening area of the other seal chamber 18b becomes smaller as it goes downward, so the rise in the liquid level in one seal chamber 18a is The drop in the liquid level in the other seal chamber 18b is greater than H.

Moreover, as the liquid level in the other seal chamber 18b decreases, the pressure receiving area is reduced, so that the seal material 1 on this side of the seal chamber 18b
The force (area×pressure) due to positive pressure applied to 6 gradually decreases.

That is, by changing the pressure receiving area of each seal chamber 18a, 18b and changing the applied pressure, each seal chamber 18a,
It is possible to suppress the liquid level change that occurs in response to the pressure difference between the sealing chambers 18b and 18b, thereby reducing the amplitude of the natural vibration of the sealing material 16, causing the sealing material 16 on the sealing chamber 18a side to overflow the side wall 15a and It is possible to prevent the liquid from flowing into the container 1.

Furthermore, even if the cover gas pressure in the furnace vessel 1 suddenly increases, the opposite effect to the above will occur.

Therefore, each seal chamber 18a, 18b increases its capacity as the liquid level rises. In other words, unless a large volume flows into the seal chamber 18a or 18b, the liquid level will not rise, so there is no risk of overflow, etc. There is no fear.

Since the amplitude of the natural vibration of the sealing material 16 is reduced, even if the cover gas pressure fluctuates, resonance will not occur in response.

° Also, in the case of this embodiment, the seal chamber 18b is isolated from the outside air by the backup seal 13, and the gas in this seal chamber 18b is sealed, so that fluctuations in the liquid level are caused by the negative pressure and pressure caused by this gas. There is also the advantage of being regulated.

In addition, in the above embodiment, both seal chambers 18a,
Although the side walls 15a, 15b of the saucer 15 are both slanted to form a chamber whose upper side expands, at least one of the chambers may be configured so that its upper side expands.

Furthermore, in the above embodiment, the saucer 1 is placed on the fixed plug 6 side.
5 and the partition plate 17 is provided on the fixed plug 9 side, however, the saucer 15 and the partition plate 17 may be provided on opposite plugs.

Furthermore, in the above embodiment, a fast breeder reactor using only one rotating plug was explained, but even if the breeder reactor is equipped with two or three rotating plugs in the radial direction,
The present invention is applicable to seals between these rotary plugs and is not limited to the embodiments.

Furthermore, it is of course possible to use liquid sealants that are dissolved at room temperature, such as mercury.

In the present invention described in detail above, a gutter-shaped saucer housing a liquid seal body is formed around the entire circumference of either the inner periphery of the opening on the furnace vessel side or the outer periphery of the rotary plug, and the gutter-shaped saucer containing the liquid seal body is formed around the entire circumference of the opening on the side of the furnace vessel or the outer periphery of the rotary plug. In a device in which a partition plate is formed around the entire circumference to be immersed in a liquid sealing material, the inside of the saucer has a structure in which the horizontal area thereof increases upwardly.

Therefore, the pressure-receiving area of the liquid seal material changes, and the force acting on it also changes, so it is possible to suppress the liquid level fluctuation of the liquid seal material that attempts to respond to fluctuations in cover gas pressure, and the amplitude of the natural vibration of the liquid seal material. As a result, fluctuations in the liquid level are regulated, and fluctuations in the liquid level no longer resonate with the period of fluctuation in gas pressure, thus preventing the sealing material from overflowing from the saucer into the inside of the furnace vessel. Problems such as contaminating the inside of the furnace and impairing various properties are eliminated.

Furthermore, leakage of the cover gas to the outside is also prevented, which has the advantage of high safety.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show one embodiment of the present invention.
The figure is a cross-sectional view showing the schematic configuration of a fast boost reactor.
The figure is an enlarged sectional view of section II in FIG. 1. 1...Reactor vessel, 2...Reactor core, 3...
... Fuel storage section, 6 ... Fixed plug, 7.
...Fuel inlet/outlet machine, 8...Opening, 9...
... Rotating plug, 10 ... Control rod drive device, 11 ... Fuel exchanger, 13 ... Backup seal, 14 ... Seal part, 15・・・
...Saucer, 16...Liquid sealing material, 17.
...Partition plate, 18a, 18b... Seal chamber.

Claims (1)

[Claims] 1. The opening at the top of the furnace vessel is shielded with a rotating plug, and a gutter-shaped saucer containing a liquid sealant is formed around the entire circumference of either the inner periphery of the opening of the furnace vessel or the outer periphery of the rotating plug, and On the other hand, in a nuclear reactor equipped with a partition plate that is immersed in the liquid sealing material in this saucer and isolates the inside and outside of the reactor vessel, the interior of the saucer is formed so that its horizontal area increases upward. A seal structure for a rotating plug in a nuclear reactor, characterized by: